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CentOS SSH Installation And Configuration

How do I install and configure ssh server and client under CentOS Linux operating systems?

You need to install the following packages (which are installed by default until and unless you removed it or skipped it while installing CentOS)

  • openssh-clients : The OpenSSH client applications
  • openssh-server : The OpenSSH server daemon

OpenSSH Installations under CentOS Linux

To install the server and client type:
# yum -y install openssh-server openssh-clients
Start the service:
# chkconfig sshd on
# service sshd start

Make sure port 22 is opened:
# netstat -tulpn | grep :22

Firewall Settings

Edit /etc/sysconfig/iptables (IPv4 firewall),
# vi /etc/sysconfig/iptables
Add the line
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
If you want to restict access to, edit it as follows:
-A RH-Firewall-1-INPUT -s -m state --state NEW -p tcp --dport 22 -j ACCEPT
If your site uses IPv6, and you are editing ip6tables, use the line:
-A RH-Firewall-1-INPUT -m tcp -p tcp --dport 22 -j ACCEPT
Save and close the file. Restart iptables:
# service iptables restart

OpenSSH Server Configuration

Edit /etc/ssh/sshd_config, enter:
# vi /etc/ssh/sshd_config
To disable root logins, edit or add as follows:
PermitRootLogin no
Restrict login to user tom and jerry only over ssh:
AllowUsers tom jerry
Change ssh port i.e. run it on a non-standard port like 1235
Port 1235
Save and close the file. Restart sshd:
# service sshd restart

See also:

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{ 16 comments… add one }
  • Oyewumi Abayomi January 22, 2011, 6:47 am




  • Abraham October 6, 2011, 6:29 pm

    Thanks very much for this info.
    This is very helpful.

    God bless you guys.

  • Darr247 December 18, 2011, 5:38 am

    There are a couple/few things I don’t get…
    e.g. for

    Make sure port 22 is opened:
    # netstat -tulpn | grep :22

    What are we *supposed* to see if port 22 *is* opened?

    And for

    Add the line
    -A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 22 -j ACCEPT

    add it *where*???
    In the :INPUT ACCEPT section?
    in the :OUTPUT ACCEPT section?
    after :COMMIT?

    No matter which line I put it on, when I restart the iptables service I get a red [FAILED] message for that line#.

    And then you change the SSH port to 1235 but don’t revisit iptables?

    What am I missing here?


  • Boymix81 February 28, 2012, 9:20 pm

    Thanks a lot!

    Only change :

    -A RH-Firewall-1-INPUT -s -m state –state NEW -p tcp –dport 22 -j ACCEPT


    -A INPUT -s -m state –state NEW -p tcp –dport 22 -j ACCEPT

    • g3g3g3 November 27, 2014, 6:05 pm

      thx a lot

  • kuldeep thakur March 15, 2012, 7:49 am

    Thanks a ton this info really very helpful for me.


  • Darr247 March 15, 2012, 11:15 pm

    Make sure port 22 is opened:
    # netstat -tulpn | grep :22

    What are we *supposed* to see if port 22 *is* open?


    • Paul Cupis April 22, 2012, 7:29 pm

      If sshd is running. you would expect to see something like:

      # netstat -plunt | grep :22
      tcp 0 0* LISTEN 70813/sshd
      tcp 0 0 :::22 :::* LISTEN 70813/sshd

      If you do not get any output where the IP/port part ends in :22, then you have nothing listening on port 22 (the standard ssh port).


  • BRAVE-MAN99 June 21, 2012, 3:07 pm

    God bliss you.
    Simple way & perfect results.

  • rkrara October 7, 2012, 11:02 am

    Some thing is wrong.
    Please help resolve it.
    The line 13 is this:
    -A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 22 -j ACCEPT

    Now when is restart iptables i get this error.

    # service iptables restart
    iptables: Flushing firewall rules: [ OK ]
    iptables: Setting chains to policy ACCEPT: filter [ OK ]
    iptables: Unloading modules: [ OK ]
    iptables: Applying firewall rules: iptables-restore: line 13 failed [FAILED]

  • pheng November 14, 2012, 2:18 pm

    change like this it will work…

    -A INPUT -m state –state NEW -m tcp -p tcp –dport 22 -j ACCEPT

  • kyferez January 26, 2013, 6:04 pm

    You missed something important: If you alter SSH Port, your iptables line –dport needs to be the same as the port you specified, not 22!

    So, if you set: Port 234, then your IP tables entry would be this:
    -A INPUT -m state –state NEW -m tcp -p tcp –dport 234 -j ACCEPT

    To verify your PROPER port is open, the command also needs to reflect the port you altered: netstat -tulpn | grep :234

    Your results should look like this:
    tcp 0 0* LISTEN 26873/sshd
    tcp 0 0 :::234 :::* LISTEN 26873/sshd

    The author should not have suggested changing the port without explaining that the commands and IPTables entries would necessitate being altered as well.

    • Kenny March 27, 2013, 4:30 pm

      I should have read this comment about 30 minutes ago… lol I was however, able to figure it out on my own. I guess that’s a good thing. :o)

  • Sagetbh June 6, 2013, 10:37 am

    Thank you so MUCH!
    This actually worked.
    You are a blessing!

  • Wellington Torrejais da Silva June 24, 2014, 2:59 pm


  • Rob March 15, 2016, 4:36 pm

    Any changes to iptables *** must *** be on lines above COMMIT, which is found at the end of the file.
    Before adding the port (eg 22), do a search to see if it already exists:
    nano iptables
    Ctrl W to invoke search
    type: dport 22

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